Class and IgG subclass distribution of antibodies against peripheral nerve myelin in sera from patients with inflammatory demyelinating polyradiculoneuropathy

Inflammatory neuropathies: pathology, molecular markers and targets for specific therapeutic intervention

Inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both. Inflammatory neuropathies may be divided into three major disease categories: Guillain-Barré syndrome (particularly the acute inflammatory demyelinating polyradiculoneuropathy variant), chronic inflammatory demyelinating polyradiculoneuropathy and nonsystemic vasculitic neuropathy (or peripheral nerve vasculitis). Despite major advances in molecular biology, pathology and genetics, the pathogenesis of these disorders remains elusive. There is insufficient knowledge on the mechanisms of hematogenous leukocyte trafficking into the peripheral nervous system to guide the development of specific molecular therapies for immune-mediated inflammatory neuropathies compared to disorders such as psoriasis, inflammatory bowel disease, rheumatoid arthritis or multiple sclerosis. The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium. This review discusses our current knowledge of the classic pathological features of inflammatory neuropathies, attempts at molecular classification and genetic determinants, the utilization of in vitro and in vivo animal models to determine pathogenic mechanisms at the interface between the systemic circulation and the peripheral nervous system relevant to these disorders and prospects for future potential molecular pathology biomarkers and targets for specific therapeutic intervention.

Guillain-Barré syndrome: clinical variants and their pathogenesis

Numerous clinical subtypes of Guillain-Barré syndrome have been described over the century since the original description of the syndrome. These variants of Guillain-Barré syndrome are discussed and their immunological pathogenesis reviewed.

Antibodies against peripheral myelin glycolipids in people with HIV infection

Plasma samples from 35 individuals with HIV infection but without clinical peripheral neuropathy were screened by ELISA for IgM and IgG antibodies against peripheral myelin. Eighteen of the 35 samples (51%) showed IgM reactivity and 11 (31%) showed IgG reactivity. By comparison, none of 48 samples from healthy blood donors showed IgM or IgG reactivity. Epitopes reacting with these antibodies were identified by TLC immunostaining as sulphatide (GalS) and the gangliosides GM1, GD1a and GD1b. Plasma samples from four people with HIV infection and neuropathy (HIV+PN), six HIV-seronegative individuals with IgM paraproteinaemic demyelinating neuropathy (IgMPDN) and 12 HIV-seronegative individuals with a variety of other neurological disorders (HIV-OND) were also investigated. Two of the four HIV+PN samples showed IgM reactivity with GalS; and two showed IgG reactivity against GalS. Of the six IgMPDN samples, three showed IgM reactivity with GalS. These data indicate that antibodies against peripheral myelin glycolipids, in particular GalS, occur more frequently in HIV infection than in HIV-seronegative individuals with and without neurological disease, and may contribute to subclinical neuropathy in HIV infection.

Peripheral nervous system (PNS) expression of mRNAs encoding myelin proteins and Fc gamma RIII during experimental allergic neuritis

Experimental allergic neuritis (EAN) was induced in Lewis rats by injection of 'SP26', a peptide homologous to amino acids 53-78 of bovine myelin P2 protein, in complete Freund's adjuvant. The rats developed signs of EAN which began on day 14, were maximal on day 18, and had subsided by day 30. RNA content of cauda equina and sciatic nerves increased more than 2-fold at the height of EAN. Expression of myelin P0 and P1 mRNAs did not fall during EAN, nor rise during recovery. Fc gamma R mRNA, which encodes Fc gamma RIII, an immunoglobulin-binding protein mediating activation of natural killer cells and macrophages by immune complexes, was transiently, but markedly induced in scattered endoneural cells, presumably macrophages, in cauda equina and sciatic nerves during the period of increasing weakness.

Immunochemical and clinical effects of immunosuppressive treatment in monoclonal IgM neuropathy

A pathogenic role of the M protein in monoclonal IgM neuropathy has been suggested. This is based among other things on a close relation between immunosuppressive treatment, lowered concentration of M protein, and clinical effect. We studied five patients with monoclonal IgM and antibodies to peripheral nerve myelin. The immunosuppressive treatment was beneficial in three of the patients. In three patients there was a relationship between antibody concentration and clinical effect (in one there was no change in antibody concentrations and correspondingly no change in clinical status, and in two patients clinical improvement corresponded to decreased antibody concentrations). In two patients, however, there was no clear correlation, since one patient improved despite increasing antibody concentrations and one patient did not improve despite a lowered antibody concentration. It is therefore possible that other mechanisms may contribute to the effect of treatment.

Expression of genes encoding receptors for IgG (FcRIII) and for C3b/C4b (Crry) in rat sciatic nerve during development and Wallerian degeneration

Northern blots were used to examine the expression of genes encoding receptors for IgG (FcRIII) and for C3b/C4b (Crry) in rat sciatic nerve during development and Wallerian degeneration. Steady state levels of FcRIII (1.4 kb) and Crry (1.9 and 2.1 kb) mRNAs were higher in adult rat nerves than in 6 day and 21 day postnatal rat nerves, indicating that the expression of these receptors is developmentally regulated. The FcRIII and Crry cDNA probes also hybridized with total RNA from 3 day old rat Schwann cells and from adult rat peritoneal macrophages. The size of the FcRIII mRNA expressed by cultured Schwann cells (1.6 kb) differed from that expressed by peritoneal macrophages (1.4 kb); the two may be splice variants of one transcript or products of related genes. Peritoneal macrophages contained approximately 100 times higher FcRIII mRNA levels than Schwann cells. In contrast, steady state levels of both 1.9 and 2.1 kb Crry mRNAs were similar in cultured Schwann cells and macrophages. Nerve transection induced a generalized increase in the level of sciatic FcRIII mRNA (1.4 kb) 3 days post-surgery, whereas the level of Crry mRNA was increased only in the nerve segment immediately to the cut. The increase of FcRIII mRNA that occurred in Wallerian degeneration was most likely due to infiltration of macrophages, as FcRIII mRNA-positive macrophages were demonstrated in the degenerating nerves by in situ hybridization. FcRIII mRNA-positive macrophages were not found in normal nerve. The functions of FcRIII and Crry in peripheral nerves are uncertain, but they may be of significance in phagocytosis, antibody-dependent cellular cytotoxicity, and in local immune regulation.

Non-receptor muscle antibodies in myasthenia gravis are of IgG1 and IgG4 subclasses

The IgG subclass distribution of non-receptor muscle antibodies was examined in 15 myasthenia gravis (MG) sera, employing an indirect haemagglutination-immunofluorescence technique. Four sera contained only IgG1, 4 contained only IgG4 and 7 contained both IgG1 and IgG4 muscle antibodies. IgG2 and IgG3 antibodies were not found. Among 11 patients with a defined thymus pathology 8 had thymoma and 3 had thymic atrophy, but there was no correlation between antibody subclass pattern and thymic pathology. Patients with both IgG1 and IgG4 antibodies tended to have the longest disease duration. We conclude that IgG non-receptor muscle antibodies in MG are of the IgG1 and/or IgG4 subclasses, irrespective of thymic pathology.

Are CSF or serum ganglioside antibodies related to peripheral nerve demyelination in neuroborreliosis, Guillain-Barré syndrome, or chronic inflammatory demyelinating polyradiculoneuropathy?

Cerebrospinal fluid (CSF) and serum IgG and IgM antibodies to seven gangliosides were determined in patients with neuroborreliosis (NB) (n = 20), Guillain-Barré syndrome (GBS) (n = 13), and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) (n = 10). The incidence of elevated antibodies was highest in NB and lowest in CIDP. Correlation between CSF and serum antibodies was only observed for IgG antibodies to GM1, GD1b and GT1b in GBS. The strong IgM antibody reactivity to gangliosides in the CSF of NB patients may be involved in the variety of neurological disorders attributed to Borrelia burgdorferi infection. Since one CIDP and three GBS patients had serologic evidence of prior or concurrent borrelia infection, this infection may belong to the infections that can trigger GBS or CIDP. The lack of specific ganglioside antibody patterns in these four patients suggests that ganglioside antibodies are not the link between Borrelia burgdorferi infection and the demyelination of peripheral nerves in GBS and CIDP.

Anti-GM1 IgA antibodies in Guillain-Barré syndrome

Serum anti-GM1 IgA antibodies were detected in 15 of 53 (28%) patients with the acute Guillain-Barré syndrome (GBS) and in one of 26 (4%) patients with other neurological diseases. Although nine GBS patients had anti-GM1 IgA titers of 1:200 or less, six patients had titers of 1:800 or more. Some GBS patients with anti-GM1 IgA antibodies also had antibodies against GD1b or GM2 or both. The presence of markedly elevated anti-GM1 IgA was associated with a poor clinical outcome at 6 and 12 months following onset of the GBS. The possible pathogenetic role of anti-GM1 IgA antibodies remains to be established.

Mapping of Fc gamma receptors in the human and porcine eye

By using an immunohistochemical technique, we detected a strong reaction product for Fc gamma receptors in the keratoconjunctival epithelium, uveal trabecular meshwork, optic nerve, and muscle walls of the retinal and ciliary vessels of infant human eyes; moderate staining was seen on the corneal endothelium, corneoscleral trabecular meshwork, non-pigmented ciliary epithelium, ciliary muscle fibers, endothelial lining of ocular blood vessels, as well as the anterior region of Muller cells, the outer nuclear layer, and pigment epithelium of the retina. In aged human and porcine eyes, the same structures stained somewhat less intensely than did those in infant human tissues. Primary cultures of porcine trabecular cells demonstrated a more intense immunoreaction product than did tertiary cultures. We discuss the possible role of Fc gamma receptors in various ocular inflammatory conditions and the implications of age-dependent expression by human trabecular cells in the pathogenesis of open-angle glaucoma.

Antibodies to peripheral nerve myelin may occur without clinical neuropathy in healthy persons

To study the role of autoantibodies against peripheral nerve myelin (PNM), sera from 255 healthy blood donors were investigated by enzyme-linked immunosorbent assay (ELISA), and persons with anti-PNM antibodies were further studied clinically and by neurography, 25 blood donors (10%) had anti-PNM antibodies of IgM, IgG or IgA isotype. The 12 blood donors with anti-PNM antibodies of IgM isotype showed only slightly decreased nerve conduction velocities compared to 12 blood donors without anti-PNM antibodies. Two blood donors with anti-PNM antibodies of IgM and IgG isotype respectively showed a clinical, previously undiagnosed polyneuropathy (PN), verified by neurography. However, also one blood donor without anti-PNM antibodies had a clinical and neurography-verified PN. We conclude that antibodies against PNM may occur in healthy persons without evidence of a clinical or subclinical PN.

Antibodies in sera from patients with inflammatory demyelinating polyradiculoneuropathy react with ganglioside LM1 and sulphatide of peripheral nerve myelin

Sera from 23 patients with acute Guillain Barré syndrome (GBS), 15 patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and from 40 age-matched blood donors were analysed for antibodies to acidic glycosphingolipids from human brain and peripheral nerve. Antibodies to ganglioside LM1, the major ganglioside of peripheral nerve myelin. were found in 43% of GBS and in 67% of CIDP patients' sera, and in 20% of the blood donors. However, antisulphatide antibodies were detected in 65% and 87% of the sera from GBS and CIDP patients, respectively, but only in 15% of the control sera. Sulphatide is the major acidic glycosphingolipid in myelin and its concentration in peripheral nerve myelin is 100 times higher than that of LM1. The high frequency of LM1 and, in particular of sulphatide antibodies, might thus be relevant to the pathogenesis of the GBS and CIDP.

Peripheral nerve CR1 limit complement-mediated haemolysis

CR1 were purified from sciatic nerve extracts by monoclonal antibody affinity chromatography. The effect of CR1 on complement-mediated haemolysis was studied by adding purified CR1 to a mixture of human serum as source of complement and sheep erythrocytes sensitized with rabbit IgG. A dose-dependent inhibition of the haemolysis occurred. There was no effect on the haemolysis when phosphate-buffered saline, elution buffer or run-through fraction not containing CR1 was added. Addition of a polyclonal anti-CR1 antibody to purified CR1 suppressed the inhibiting activity, strongly indicating that peripheral nerve CR1 inhibit complement-mediated haemolysis. This may be of great importance in vivo since CR1 present on the Schwann cell membrane may prevent the formation of terminal lytic complexes.

Plasma exchange in Guillain-Barré syndrome: effect on anti-peripheral nerve myelin antibodies

Increased levels of anti-peripheral nerve myelin (anti-PNM) antibodies were demonstrated by ELISA in serum from 4 of 7 patients with Guillain-Barré syndrome (GBS). Treatment with plasma exchange (PE) was performed and 6 of the 7 patients showed clinical improvement with marked increase in muscular strength. One patient, however, continued to deteriorate during the treatment. No correlation between clinical improvement and levels of anti-PNM antibodies was observed. Whether the antibodies are of pathogenetic importance in GBS is therefore still unknown.

Neuropathy and myopathy in primary Sjögren's syndrome: neurophysiological, immunological and muscle biopsy results

Seventeen consecutive patients with primary Sjögren's syndrome (PSS) received neurophysiological examination, analysis of antibodies against peripheral nerve-myelin (PNM) and muscle biopsy, to show the prevalence and characteristics of peripheral neuropathy (PN) and myopathy; 3 PSS cases showed a clinical mild sensorimotor polyneuropathy, 1 of them had been treated with cytostatic drugs; 1 had mononeuropathia multiplex; and 1 clinical carpal tunnel syndrome. In these 5 patients neurophysiological investigation verified the clinical diagnosis of peripheral nerve involvement; 2 with PN had serum-antibodies against PNM; 1 of IgM-, and 1 of IgA-isotype. Muscle biopsies were taken from 15 PSS patients; 11 showed inflammatory myositis or inflammatory perivascular infiltrates and 3 showed signs of denervation. A combination of inflammation and morphological signs of myopathy, compatible with the biopsy diagnosis of polymyositis, was seen in 4, 1 of whom showed clinical signs of polymyositis. We conclude that the peripheral nervous and muscular systems are often involved in PSS, but commonly with relatively mild symptoms and laboratory findings. The common findings of inflammatory myopathy indicate an immune reaction in muscles in addition to other autoimmune manifestations of the disease.

Peripheral nerve CR1 express in situ cofactor activity for degradation of C3b

Adsorption of sheep erythrocytes (E) sensitized with IgM antibodies (A) and C3b (EAC3b) to C3b/C4b receptors (CR1) in cryostat sections of human myelinated nerves was studied using the closed chamber technique. The adsorption was stable for at least 3 h at 37 degrees C. In the presence of purified factor I, the indicator cells detached from the sections after 40 min at 37 degrees C. Factor H was not required. The release was not due to loss of CR1 activity in the sections. The detached indicator cells were negative in the immune adherence test and were agglutinated by antibody to C3d, but not by antibody to C3c. Western blot of the detached indicator cells revealed the presence of C3d and C3c was found in the chamber fluid. Accordingly, detachment of the indicator cells was due to degradation of C3b to C3d with the release of C3c into the chamber fluid. Protease inhibitors did not prevent the detachment of the indicator cells. EAC3b incubated with sections of myelinated nerves pre-incubated with anti-CR1 antibody or with sections of unmyelinated nerves which contain functionally inactive CR1 were not degraded. The results therefore indicate that CR1 in situ in myelinated nerves can provide the necessary cofactor activity for factor I-mediated degradation of C3b to C3d and C3c.

Localization of Fc gamma receptors and complement receptors CR1 on human peripheral nerve fibres by immunoelectron microscopy

The localization of receptors for the Fc part of IgG (Fc gamma R) and for the complement C3b/C4b components (CR1) on human peripheral nerve fibres was investigated by indirect immunoperoxidase staining of frozen nerve sections with monoclonal antibodies. Transmission electron microscopy revealed that Fc gamma R and CR1 are localized to the entire surface membrane and inner membrane (axolemma) of the Schwann cell. Myelin and axons were not stained. The presence of Fc gamma R and CR1 in human Schwann cells adds further evidence for the immunocompetence of these cells.